Tall

Re Size Up - Not used it. Looks fine from the description. I'm assuming frm this you want to mass up?

Re Bench - Take it in baby steps and add a little bit more weight to the bar each week, make sure your form is good (i.e. the chest is doing the heavy work, not your arms)

Re chest : My advice on this would be to do couple of warm up sets - bar only in the high rep range, and then start with a weight set and rep range you feel comfortable with - maybe 3 sets of 8-10 and 45kg.

The next week do the warm up, and try upping the weight and aiming for 6-8 reps, maybe 47.5kg or 50kg.

The next week warm up, and work in the lower rep ranges - 4 to 6 reps - and up the weight on the bar. Then try and see what you can press for 1rep.

Make sure you use a spotter...

That should give you a good idea of where you are and what your range of lifting is.

Then each week try and up the weight on a rep range you are happy with until you reach your goal. I like to mix my reps around each week which I find works for me, but it may not work for you. Everyone is different.

You need to find what works for you at the end of the day.

Re Weight Gain - get eating. 10kg is alot of pack on. It can be done dont get me wrong. You need to eat like a horse and workout properly.

Odds are you may/will gain some fat in the process.

Fire up your diet and routine - theres alot of good guys on the board who will be able to help you.